Self-describing real-time device data communication system

ABSTRACT

An implantable medical device (IMD) communicates with an external processing unit by transmitting device data and configuration information that describes the device data. The external processing unit processes the device data for display based on the configuration information. The IMD notifies the external processing unit of a change to characteristics of the device data by transmitting the changed device data and updated configuration information.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit of U.S. Provisional Application No.60/589,253 filed Jul. 20, 2004 for “Self-Describing Real-Time DeviceData Communication System” by R. Hanson, C. Petersen, R. Klepfer, M.Rochat, J. Ericksen, C. Stomberg and A. Koenigsfeld.

INCORPORATION BY REFERENCE

The aforementioned U.S. Provisional Application No. 60/589,253 is herebyincorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a system for communicating data betweenan implantable medical device (IMD) and an external processing unit.

Since the introduction of the first implantable pacemakers in the 1960s,there have been considerable advancements in both the field ofelectronics and medicine, such that there is presently a wide assortmentof commercially available body-implantable electronic medical devices.The class of IMDs now includes pacemakers, implantable cardioverters,defibrillators, neural stimulators, and drug administering devices,among others. Today's state-of-the-art IMDs are vastly moresophisticated and complex than early ones, and are capable of performingsignificantly more complex tasks. The therapeutic benefits of suchdevices have been well proven.

It has proven useful for IMDs to have the capability of communicatingdata with an external processing unit that in turn has the ability toprocess, store and/or display data provided by the device. The dataprovided by the device may be real-time or recorded data. The externalunit may also transmit signals to the implanted medical device in orderto provide some control over the device. This communication is achievedby wireless telemetry, the physical characteristics of which are knownin the art.

Existing implantable medical device systems have relied on the externalprocessing unit to initiate data communication with the IMD, at least inpart due to processing limitations of the IMD. A typical scenario insuch a system is as follows:

-   -   (1) “Wake up” implantable device, such as with wireless        transmission, a magnet, or other initiating means.

(2) Implantable device transmits device identification information.

(3) External processing unit identifies device and loads appropriateapplication program.

(4) External processing unit interrogates implantable device todetermine configuration of device, such as type or format of data thatwill be transmitted, etc.

(5) Implantable device transmits data to external processing unitaccording to format and configuration established.

(6) External processing unit initiates change in data type or format tobe transmitted by implantable device by transmitting command to device.

(7) Implantable device adjusts the type or format of the datatransmission.

This communication scenario illustrates the necessity, in existingsystems, of a specific application program for each type of device andfor each data characteristic (data type, structure or format) supportedby the device, so that proper manipulation of the raw data transmittedby the implantable device can be done according to the configurationdetermined by the external processing unit by interrogation. While thesesystems have provided excellent results in situations where applicationprograms and IMDs are specifically designed to work together, it wouldbe useful to provide a system in which at least some level of datacommunication and cooperation is available even when the applicationprogram is not specifically designed for a particular IMD or datacharacteristic.

BRIEF SUMMARY OF THE INVENTION

The present invention is a system and technique for communicatingbetween an implantable medical device (IMD) and an external processingunit. The IMD transmits device data and configuration information thatdescribes the device data. The external processing unit processes thedevice data for display based on the configuration information. The IMDnotifies the external processing unit of a change to a characteristic ofthe device data by transmitting the changed device data and updatedconfiguration information.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating the basic functional componentsof an implantable medical device and an external processing unit.

FIG. 2 is a flow diagram illustrating the basic communication scheme ofthe present invention.

FIG. 3 is a functional block diagram illustrating a system forcommunication between an implantable medical device and an externalprocessing unit in the manner described with respect to FIG. 2.

DETAILED DESCRIPTION

FIG. 1 is a block diagram illustrating the basic functional componentsof implantable medical device (IMD) 10 and external processing unit 12.IMD 10 includes sensor/operating circuitry 14, processing circuitry 16,memory circuitry 18, and communication circuitry 20. External processingunit 12 includes communication circuitry 22, processing circuitry 24,active application 25 including active loaded program 26 and desktopapplication 27, and stored/non-active application(s) 28. Communicationcircuitry 20 of IMD 10 and communication circuitry 22 of externalprocessing unit 12 communicate with one another over wireless link 29,which may be a radio frequency (RF) link or another suitable type ofwireless communication.

In operation, IMD 10 is capable of transmitting data relating to theoperation of sensor/operating circuitry 14 and data relating to itsconfiguration stored in memory circuitry 18 over wireless link 29 toexternal processing unit 12. IMD 10 is also capable of receivingprogramming information and other communication from external processingunit 12 to control the operation of sensor/operating circuitry 14 and todirect communication between IMD 10 and external processing unit 12.External processing unit 12 is capable of processing the data receivedfrom IMD 10 according to an appropriate application program.Specifically, external processing unit 12 receives configurationinformation from IMD 10, and loads an appropriate application program(active loaded program 26) for execution. Active loaded program 26 isable to properly manipulate and/or display the operation data that istransmitted by IMD 10, while other programs (stored/non-activeapplication(s) 28) that are not suited for manipulation and/or displayof the operation data are simply stored and not loaded for execution byexternal processing unit 12.

As discussed previously, the existing procedure for establishing andadjusting communication of operation data between IMD 10 and externalprocessing unit 12 requires external processing unit 12 to control thecommunication session, and requires execution of active loaded program26 in order to properly manipulate and/or display data received fromimplantable medical device 10. Users are therefore required to wait forexternal processing unit 12 to load and execute the appropriateapplication program before any data can be viewed, even though IMD 10may already be transmitting the data. This often can take 20 seconds ormore, which is at the very least an annoyance for the user. Moreover, ifan appropriate application program is not available for loading byexternal processing unit 12, then no manipulation and/or display of datafrom IMD 10 is possible.

The present invention provides a communication scheme in which operationand configuration data is self-describing. This self-describing dataallows each type, structure or format of data to be independentlyprocessed by the external processing unit. As a result, a system isconfigured in which the external processing unit is always able tomanipulate and/or display at least some data, regardless of whether aspecific application program is available that corresponds exactly tothe type of IMD or to the type, structure or format of data beingtransmitted. For example, desktop application 27 may include sufficientcapability to process and display certain basic data transmitted by anIMD. The term “desktop application” refers to any application that iscontinually executed, often in the background, on a computer system.Desktop applications are typically limited in their capabilities becauseof the desire to limit the system resources that they require, so thatthe computer system can execute other applications quickly and smoothly.However, the ability of the present invention to transmitself-describing data from an IMD allows desktop application 27 toprocess and display as small of a set of data characteristics (datatypes, structures and formats) as desired, within the limits of thesystem resources available. Because desktop application 27 iscontinually running in the background, it can process and displaysupported data types immediately, without having to wait to load aspecific application program. The program that is processing anddisplaying data, whether it be desktop application 27 or active loadedprogram 26, may have the ability to adapt to a change in the datacharacteristics and configuration without necessarily having to switchto another active program.

FIG. 2 is a flow diagram illustrating the basic communication scheme ofthe present invention. Communication by an IMD begins at Start block 30,initiated by the presence of a magnet, an instrument downlink request,or some other initiation mechanism. Upon initiation of communication,the IMD transmits, or “beacons,” waveform data and configuration data asindicated at block 32. During this beaconing stage, configuration datais transmitted at a relatively high rate (frequency of occurrence), suchas once per second in an exemplary embodiment. The beaconing stagecontinues until a telemetry session is established between the IMD andthe external processing unit, as indicated by decision block 34. Oncetelemetry has been established, the IMD continues to transmit waveformdata according to the configuration that has been previouslycommunicated, as indicated at block 36. Configuration data may betransmitted occasionally from the IMD to the external processing unit inthis stage, but at a lower rate than during the beaconing stage. The IMDcontinues to transmit waveform data until a change in configuration isdesired, as indicated at decision block 38. When a change inconfiguration is to occur, the IMD transmits waveform data according tothe new configuration and transmits configuration data to the externalprocessing unit, as indicated at block 0.39. The new configuration datais again transmitted at a relatively high rate in order to ensure thatit is received properly by the external processing unit. After theconfiguration has been successfully changed, the IMD transmits waveformdata having characteristics that correspond to the new configuration, asindicated at block 36.

The physical beaconing transmission by the IMD is accomplished in thesame manner as for previous systems, where IMDs beaconed only basicdevice identification information. The system of the present inventionallows the IMD to beacon essentially all of its information, bytransmitting device identification information, waveform data, andconfiguration information that describes the waveform data beingtransmitted.

The communication of configuration information by the IMD isparticularly useful in an ambulatory setting, where the externalprocessing unit is a monitor that is only capable of receivingtransmissions from the IMD and storing data, and is not capable oftransmitting information back to the device. In fact, some monitors donot even have the ability to process the data received from the IMD, butsimply store (or immediately transfer) the data received for laterprocessing and/or display by a separate system component (which servesas the external processing unit in this type of system). While this typeof limited monitoring is not typical for most clinic-based medical datacommunication systems, there are some applications in which such anambulatory monitor may be employed, such as an in-home monitor thatreceives data from an IMD and transmits the data over a communicationnetwork for review by a caregiver at a remote location.

In the ambulatory setting, telemetry sessions are not necessarily“established” in the manner described in block 34 of FIG. 2. Thus, theIMD transmits configuration information at a constant (high) rate,rather than reducing the rate after establishment of a telemetrysession. In prior ambulatory monitoring systems, the external processingunit needed to be pre-configured to receive a particular kind of datafrom an IMD or monitor, to ensure that the external processing unit wasrunning an application program that could process and display the data.Any changes in the data characteristics (data type, structure or format)required re-configuration before the new data could be displayed, orinterrogation of the IMD afterward to determine what data configurationchanges had occurred. By transmitting configuration information from theIMD that describes the data being transmitted, a monitor is able tostore the data and its associated configuration information, and anexternal processing unit can display all data that it understands,dynamically adjusting to different data characteristics without the needfor re-configuration.

FIG. 3 is a functional block diagram illustrating an exemplary systemfor communication between IMD 40 and an external processing unit, in themanner described above with respect to FIG. 2. The functional blockdiagram of FIG. 3 includes blocks that represent actual components andsignals (IMD 40, telemetry subsystem, 41, surface electrode cardiacsignals 45, user interface/display 46, chart recorder 49) and functionalblocks that represent software or other circuitry that is configured toperform certain functions (functional blocks 42, 44 and 48).

IMD 40 communicates all telemetry data with telemetry subsystem 41,which may be incorporated into the external processing unit or may be aseparate communication module. Telemetry subsystem 41 parses the datareceived from implantable device 40, as indicated by functional block42. The data received from implantable device 40 includes waveform datarepresenting cardiac signals, markers indicating the occurrence ofparticular cardiac or device events, and markers that includeconfiguration information. The markers are referred to as “supplementalmarkers,” which are data records within a frame of transmitted data thathave been used in the past to mark and describe cardiac events or tomark particular moments in time. The present invention utilizes a newtype of supplemental marker (a configuration supplemental marker), in aformat similar to existing supplemental markers so that it is able to beparsed by existing systems, that conveys configuration informationrelating to the waveform data transmitted by the IMD. The parsed data isthen utilized by application software, as indicated by functional block44, to properly display the waveform data. Specifically, the event andconfiguration supplemental markers are used to properly label thewaveform data and to display the waveform data in an appropriate format.The application software also is able to receive data from anothersource, such as surface electrode cardiac (ECG) signals 45, to provide adisplay on user interface 46 that includes the data from implantabledevice 40 as well as the ECG signals.

The parsed data from functional block 42 is also utilized to displaywaveform data on chart recorder 49, as indicated at functional block 48.Similar to the application software (functional block 44), the event andconfiguration supplemental markers are used to properly label thewaveform data and to display the waveform data in an appropriate format.ECG signals 45 are also utilized, to provide a display on chart recorder49 (or any real-time storage or display device) that includes the datafrom implantable device 40 as well as the ECG signals.

In order to support the transmission of configuration information fromthe IMD, accommodations in the communication packet format are made.Generally speaking, the IMD transmits data to the telemetry subsystemassociated with an external processing unit in fixed data windows (alsoreferred to as communication frames), so that communication can occur ina structured manner. These windows include large reserved bandwidth forsupplemental markers and accommodate the additional supplemental markersfor configuration information according to the present invention. Anexemplary data window for communication of data (including configurationinformation) by an IMD is shown below in Table 1. TABLE 1 WaveformPacket Reserved Supplemental Markers Arbitration Bandwidth ConfigurationEvents Information

The waveform packet includes the cardiac data measured by theimplantable device, and also will indicate when a change toconfiguration information associated with the data occurs, by includinga configuration identification number that corresponds to aconfiguration number of the supplemental marker that described the mostup to date configuration. The configuration identification number islocated at the end of the waveform packet, as the last data byte. Thisallows the implantable device to begin sending waveform dataimmediately, before the entire waveform packet is constructed (e.g.,before it is known whether there are configuration supplementalmarkers). Also, if the construction of the waveform packet changes, theconfiguration byte will still be identifiable at the end of the packet.In an alternative embodiment, the supplemental markers, includingconfiguration information and/or events, may be transmitted before thewaveform packet; it will be understood by those skilled in the art thatvarious arrangements of the data window are possible. An example of asuitable waveform packet construction is shown below in Table 2. TABLE 2Data Length Minimum length Maximum length Channel 1 data  8 bytes(always  8 bytes  8 bytes configured) Channel 2 data  8 bytes (always  8bytes  8 bytes configured) Channel 3 data  8 bytes (if  0 bytes  8 bytesconfigured) Channel 4 data  8 bytes (if  0 bytes  8 bytes configured)Marker Data 12 bytes (always 12 bytes 12 bytes configured) Configuration 1 bytes  1 bytes  1 bytes Total 29 bytes 45 bytes

The configuration byte consists of four bits reserved for future use(for example, to indicate the type of implantable device) and four bitsused for the configuration identification number.

The configuration supplemental markers (CSMs) transmitted by theimplantable device contain the information needed to decode the waveformdata transmitted by the device in the waveform packets. The informationcontained in the CSMs may or may not be different for different types ofimplantable devices; the CSMs are tied to the waveform datacharacteristics, not the device type. The CSMs are transmitted during acommunication session between the implantable device and an externalprocessing unit on the order of once per second, unless a condition ispresent that dictates more or less frequent transmission. Theseconditions include the presence of a magnet and a recent change to anyof the configuration information, for example. CSMs are transmitted intheir entirety, rather than only transmitting information that changedfrom the last CSM, so that there is no danger of error should a previousCSM have been missed by the external processing unit. CSMs also have anidentification associated with them that identifies these types ofmarkers uniquely from other types of event supplemental markers thathave been used in previous telemetry systems, so that the externalprocessing unit can properly recognize CSMs separately from othersupplemental markers.

Typically, CSMs are transmitted as the first supplemental marker in thesupplemental marker window, as shown above in Table 1. However, itshould be understood that the CSMs may be given a lower priority in someapplications, and may occur later in the supplemental marker window.

One benefit of transmitting configuration information in a CSM is thatconfiguration information can be sent at relatively infrequentintervals. This saves communications bandwidth and device battery power,both of which are at a premium in some applications. While it is alsopossible to transmit configuration information with every item of datathat is transmitted, throughput would be decreased in such a systemcompared to the system that employs CSMs as described herein.

In one embodiment, the CSMs convey information in a tag/value protocol.Each piece or group of pieces of configuration information isrepresented by a tag. The implantable device knows all the tags andvalues it can generate, and the external processing unit knows thesuperset of all the tags that any implantable device with which it iscompatible can generate. The tag is the key used by the externalprocessing unit and its associated software to decode the value thatfollows the tag. When a new tag is created, the portions of the softwaredealing with the old tags do not need to change, and therefore do notneed to be retested. A new tag ID can just be added to the code. In thisway, the external processing unit software can be modularized tominimize the impact of future changes. This reduction of the testingburden means that the external processing unit software can simply beupdated when a new IMD application is released. This provides superiorflexibility over a system in which the data configuration information ishard coded. The flexibility of the tag approach also allows futuremodifications to be easily accommodated, and relieves softwaredevelopers from having to determine all possible configurationinformation that may at some point in the future be useful or desirableto support.

Tags describing configuration data are placed in CSMs (rather than inthe waveform packet itself) at least in part because of the flexiblelength of supplemental markers. The impact on the waveform data in thewaveform packet is minimized by communicating configuration informationin a separate type of packet. This is particularly important in systemswhere the hardware constructs the waveform packet in such a way thatthere is virtually no ability to vary the length of the waveform packet.

In describing the configuration of waveform data, there are some naturalgroupings that all applications, present and future, typically need tospecify. For example, it is almost always necessary to specify thesource, gain, and sampling rate of each channel. The number of tags thatare used can be minimized by grouping some of these characteristicstogether in the same tag. If data provided by future devices requiresthe groupings to be separated, that can be done as well.

Each CSM includes a supplemental marker header and at least one tag. Thesupplemental marker header is similar to the marker headers that havebeen used in existing products, so that the telemetry system is able torecognize it as a supplemental marker header and parse itsidentification information.

If the external processing unit receives a tag from an implantabledevice that it does not understand, the tag is ignored. Thus, data froman implantable device that is understood can be displayed, even when theexternal processing unit does not support all of the functionality ofthe particular implantable device that is employed.

The following tables describe examples of particular tags that might beused in a typical system. Tag 0 (contains configuration ID that linksthe supplemental marker to the waveform packet B will always be in theconfiguration supplemental marker) Type of Bit Tag Level Trans-Description ID Length lation Table Notes Configuration 0 1 byte IntegerID Tag Configuration 1 byte Integer First 4 bits reserved, ID Numbersecond 4 bits represent configuration ID (changes every timeconfiguration changes) Standard 1 byte Integer Indicates system Versionprotocol version, to specify how supplemental markers are to be parsed

Tag 1 (contains information that is basic to the implantable device, andcan't change within a session B allows telemetry system to parsewaveform packet) Type of Bit Tag Level Trans- Description ID Lengthlation Table Notes General Data 1 1 byte Integer Config Tag Number of 4bits Integer Channels Master 2 bytes Hertz Sampling rate of all SamplingRate (numeric) channels, if common. Used as default in absence ofspecific sampling rate for each channel. Total # of Data 1 byte IntegerDoes not include the Samples in markers. Waveform Packet Bytes of 1 byteInteger Marker Data Marker 4 bits Lookup Index Specifies marker Schemecharacteristics, such as where markers are located in waveform packet,how markers are aligned to data samples, keys for decoding markervalues, whether marker bytes per packet are fixed or variable, etc.

Tag X (created for each channel, where channels have individualizedcharacteristics) Tag Type of Bit Level Description ID Length TranslationTable Notes General X 1 byte Integer Channel Config Tag SubsamplingHertz Rate of Channel Channel Integer Number Packed/Non- Boolean Arethere empty spots packed Data (non-packed) or not Scheme (packed) in thesubsampling?

Tag 2 (general tag to describe basic channel parameters) Type of Bit TagLevel Trans- Description ID Length lation Table Notes Channel 2  1 byteInteger Device Basics Tag Channel  4 bits Integer Number Source Name 12bits Lookup index Link to a table of strings Amplifier Gain 20 bitsNumeric May also need to (value) include offset for channels providingpressure data, or the high pass filter pole of a channel. Amplifier Gain 1 byte Numeric The multiplier for (exponent) waveform data to yield theactual data value. Includes one bit for sign. Units 12 bits Lookup indexBased on the type of data (pressure, temperature, voltage, etc.)

Tag 3 (a generic tag used to describe basic display parameters for achannel Type of Bit Tag Level Trans- Description ID Length lation TableNotes Channel 3 1 byte Integer Display Basics Tag Channel 4 bits IntegerNumber Location on X bits Numeric Typically in millimeters Screen Printon Strip 1 bit Boolean Yes or no. Chart? Strip Chart X bits Numeric Gain

In one embodiment, a CSM that would provide sufficient configurationinformation includes the following: Configuration tag  3 bytes (tag 0)General Data Configuration tag  6 bytes (tag 1) Channel Device Basicstag (8 bytes per channel × 4 channels =) (tag 2) 32 bytes Total 41 bytes

The present invention, as described above with respect to exemplaryembodiments, provides the ability for an IMD to transmit data that isself-describing. Configuration information is transmitted by the IMD ona dynamic basis that describes the data being transmitted and thatincludes the information needed for an external processing unit todecode the data for proper manipulation, storage and/or display. As aresult, data can be received and decoded by the external processing unitimmediately after an IMD is “woken up,” eliminating the need to wait fora device-specific application program to load before data can bedisplayed. In addition, the characteristics of the data provided by theIMD can be adjusted dynamically, based on conditions of the data itself,time or other factors, without the need for the external processing unitto initiate such a change. This flexibility is useful for ambulatorymonitoring as well, such as an in-home monitoring system.

The present invention may find application in a wide variety ofscenarios involving communication between an IMD and an externalprocessing unit. The ability of the IMD to transmit data that isself-describing, so that it can recognized and interpreted withoutpre-configuration of the receiving device, allows a number of potentialsituations to be readily handled. For example, dynamic changes in thecharacteristics of data being transmitted by the IMD are recognized bythe external processing unit by virtue of the configuration informationthat the IMD transmits along with the data. Changes to characteristicsor parameters of the data, such as the type, structure or format of thedata, are reflected on the display of the external processing unitnearly instantaneously. Data is displayed properly even wheninterruptions in telemetry occur, due to the IMD's transmission ofconfiguration information with its data. The external processing unitadjusts its display in response to configuration information that isreceived with the data, rather than simply making a change in responseto a request for a data characteristic change. Basic data (e.g.,waveform data) is interpreted by an external processing unit for displayeven when an application program specific to the IMD or datacharacteristics is not available. A generic waveform display instrument,such as a hand-held personal data administrator, personal digitalassistant (PDA), program, or the like, is usable with the presentinvention to allow the user to see waveforms and associated labels forany implantable device.

Portions of the above description include specific details that areprovided in order to clearly illustrate the principles of the presentinvention, but which should not be understood as limitations of thepresent invention. For example, a tag and value protocol is described toillustrate a possible implementation of a system in which an IMDtransmits configuration information to an external processing unit thatidentifies cardiac data. Those skilled in the art will appreciate thatother approaches may be used to accomplish this function, whileretaining at least some of the benefits described herein. In addition,an exemplary data window has been described in which waveform datapackets and supplemental markers are transmitted by an IMD. It should beunderstood that other configurations of data windows may be implementedthat could include the same or similar data that is communicatedaccording to the present invention, and the present invention should notbe understood as limited to the particular data structure disclosedherein. Other variations from the embodiments disclosed, while achievingthe purposes and principles of the present invention, will be apparentto those skilled in the art.

The description above has also typically described data transmitted bythe IMD as waveform data. While this description is appropriate for mosttypes of data, which are displayed as a waveform on the display of anexternal processing unit, there may be some types of data that aredisplayed in another manner and therefore might not be referred to aswaveform data. Thus, as used herein, the term “waveform data” should beunderstood to include any type of data transmitted by the IMD thatrepresents characteristics and parameters that are measured or otherwisedetermined by the device, and this data may also be referred to morebroadly as “device data” or “medical data.”

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

1. A method for communicating between an implantable medical device(IMD) and an external processing unit, the method comprising:transmitting device data and configuration information from the IMD;processing the device data for display at the external processing unitbased on the configuration information; and notifying the externalprocessing unit of a change to characteristics of the device data bytransmitting the changed device data and updated configurationinformation from the IMD.
 2. The method of claim 1, wherein the externalprocessing unit executes a desktop application for processing at leastsome of the device data and loads an active program for execution inresponse to the configuration information received from the IMD.
 3. Themethod of claim 1, wherein transmitting device data and configurationinformation from the IMD and notifying the external processing unit of achange to the characteristics of the device data comprises: transmittingdevice data in a first data packet; and transmitting configurationinformation in a second data packet.
 4. The method of claim 3, whereinthe first data packet and the second data packet are transmitted in acommon communication frame.
 5. The method of claim 3, wherein the firstand second data packets include a configuration identifier correlatingthe device data with the configuration information.
 6. The method ofclaim 3, wherein transmitting device data and configuration informationfrom the IMD and notifying the external processing unit of a change tothe characteristics of the device data further comprises: transmittingmarkers that provide information to label the device data for display.7. The method of claim 3, wherein the configuration information isstructured as at least one tag having a tag identifier and at least onevalue representing a data parameter.
 8. The method of claim 7, whereinthe at least one tag is selected from a plurality of predefined tags,each of the predefined tags including a plurality of values representingdata parameters that are grouped together in the predefined tag.
 9. Themethod of claim 1, wherein processing the device data for display at theexternal processing unit based on the configuration information includesprocessing the device data for display on a chart recorder.
 10. A methodfor communicating between an implantable medical device (IMD) and anexternal processing unit, the method comprising: transmittingconfiguration information from the IMD; transmitting device data fromthe implanted medical device, the device data including an indicator ofthe configuration information that is to be associated with the devicedata; comparing, at the external processing unit, the configurationinformation most recently received from the IMD to the indicator in thedevice data of the configuration information that is to be associatedwith the device data; and processing the device data based on theconfiguration information, upon determining that the configurationinformation most recently received from the IMD corresponds to theindicator in the device data of the configuration information that is tobe associated with the device data.
 11. The method of claim 10, whereintransmitting configuration information and device data from the IMDcomprises: transmitting device data, including the indicator of theconfiguration information that is to be associated with the device data,in a first data packet; and transmitting configuration information in asecond data packet.
 12. The method of claim 11, wherein the first datapacket and the second data packet are transmitted in a commoncommunication frame.
 13. The method of claim 11, wherein transmittingconfiguration information and device data from the IMD furthercomprises: transmitting markers that provide information to label thedevice data for display.
 14. The method of claim 11, wherein theconfiguration information is structured as at least one tag having a tagidentifier and at least one value representing a data parameter.
 15. Themethod of claim 14, wherein the at least one tag is selected from aplurality of predefined tags, each of the predefined tags including aplurality of values representing data parameters that are groupedtogether in the predefined tag.
 16. A method for communicating betweenan implantable medical device (IMD) and an external processing unit, themethod comprising: initiating communication by the IMD; transmittingdevice data and configuration information from the IMD in a beaconingprocedure, the configuration information being transmitted at a firstrate; determining whether the configuration information is to bechanged; and upon determination that the configuration information is tobe changed, transmitting device data and configuration information fromthe IMD in a manner where the configuration information is transmittedat the first rate.
 17. The method of claim 16, further comprising:during transmission of device data and configuration information fromthe IMD in the beaconing procedure, determining whether a telemetrysession has been established between the IMD and the external processingunit; and upon determination that a telemetry session has beenestablished between the IMD and the external processing unit,transmitting device data and configuration information from the IMD in amanner where the configuration information is transmitted at a secondrate lower than the first rate.
 18. A system comprising: an implantablemedical device (IMD) operable to transmit device data and dynamicallyupdated configuration information that describes the device data beingtransmitted; and an external processing unit operable to receive thedevice data and configuration information from the IMD and to processthe device data for display based on the dynamically updatedconfiguration information.
 19. The system of claim 18, furthercomprising: a monitor operable to receive the device data andconfiguration information transmitted by the IMD, store the device dataand configuration information received from the IMD, and transmit thedevice data and configuration information to the external processingunit, so that the external processing unit receives the device data andconfiguration information from the IMD via the monitor.
 20. The systemof claim 18, wherein the external processing unit executes a firstapplication program for processing at least some of the device data andloads a second application program for execution in response to thedynamically updated configuration information received from the IMD. 21.The system of claim 18, wherein the IMD is operable to transmit devicedata and configuration information in at least one communication framecomprising: a first data packet including the device data; and a seconddata packet including the configuration information.
 22. The system ofclaim 21, wherein the first and second data packets include aconfiguration identifier correlating the device data with theconfiguration information.
 23. The system of claim 18, wherein thesecond data packet further includes markers that provide information tolabel the device data for display.
 24. The system of claim 18, whereinthe configuration information is structured as at least one tag having atag identifier and at least one value representing a data parameter. 25.The system of claim 24, wherein the at least one tag is selected from aplurality of predefined tags, each of the predefined tags including aplurality of values representing data parameters that are groupedtogether in the predefined tag.
 26. The system of claim 18, furthercomprising a chart recorder for displaying the device data.
 27. Animplantable medical device (IMD) comprising: sensor circuitry formeasuring medical data; processing, memory and communication circuitryoperable to transmit to an external processing unit the measured medicaldata and dynamically updated configuration information that describesthe medical data being transmitted.
 28. The IMD of claim 27 wherein theprocessing, memory and communication circuitry is operable to transmitthe medical data and configuration information in at least onecommunication frame comprising: a first data packet including themedical data; and a second data packet including the configurationinformation.
 29. The IMD of claim 28 wherein the first and second datapackets include a configuration identifier correlating the device datawith the configuration information.
 30. The IMD of claim 28, wherein thesecond data packet further includes markers that provide information tolabel the medical data for display.
 31. The IMD of claim 28, wherein theconfiguration information is structured as at least one tag having a tagidentifier and at least one value representing a data parameter.
 32. TheIMD of claim 31, wherein the at least one tag is selected from aplurality of predefined tags, each of the predefined tags including aplurality of values representing data parameters that are groupedtogether in the predefined tag.
 33. An external processing unit forreceiving and displaying transmitted medical data, comprising:communication circuitry operable to receive the medical data anddynamically updated configuration information that describes the medicaldata; a first application program for processing and displaying at leastsome of the received medical data based on the dynamically updatedconfiguration information; and a second application program loaded inresponse to the dynamically updated configuration information to processand display the received medical data.
 34. The external processing unitof claim 33, wherein the second application program is loaded byselecting the second application program from a plurality of storednon-active programs based on the dynamically updated configurationinformation.
 35. An external processing unit for receiving anddisplaying transmitted medical data, comprising: communication circuitryoperable to receive the medical data and dynamically updatedconfiguration information that describes the medical data; and anapplication for processing and displaying the received medical databased on the dynamically updated configuration information, theapplication being operable to adjust its processing and display inresponse to the dynamically updated configuration information.